There are two copending patent application from the author of the present invention contents of which are hereby incorporated herein by reference; first Copending PCT Patent Application Serial Number PCT/IL2004/000659, filed Jul. 20, 2004 entitled, “ADAPTIVE RESYNCHRONIZATION THERAPY SYSTEM”, published Apr. 14, 2005, under publication number WO 2005/007075; second Copending PCT Patent Application Serial Number PCT/IL2006/000571, filed May 15, 2006 entitled, “VENTRICLE PACING DURING ATRIAL FIBRILLATION EPISODES”.
Implanted cardiac stimulation devices, i.e. pacemakers and intracardiac cardioverter defibrillators (ICD) deliver therapy to patients suffering from various heart-diseases (Clinical Cardiac Pacing and Defibrillation, 2nd edition, Ellenbogen, Kay, Wilkoff, 2000). Dual chamber pacemakers stimulate the right ventricle with synchrony to the sensed atrial event, with a given delay, the atrioventricular (AV) delay. Cardiac Resynchronization Therapy (CRT) devices, e.g., biventricular pacemakers, stimulate both ventricles and also synchronize the stimulation in correspondence with the sensed atrial event signal. With all implanted cardiac stimulation devices the management of the stimulation according to the accurate sensing and interpreting the electrical activity of the heart in the atria and in the ventricles is crucial for the variety of stimulation methods and algorithms. U.S. Pat. No. 6,901,291 disclose a method to distinguish between valid and invalid cardiac senses. U.S. Pat. No. 6,862,471 discloses a method for blanking T-waves from atrial cardiac signals. U.S. Pat. No. 6,912,418 discloses a system for distinguishing electrical events originating in the atria from far-field electrical events originating in the ventricles. U.S. Pat. No. 6,731,978 discloses a prioritized rule based method for detection, classification and treatment of arrhythmias.
Generally, these methods are related to the timing cycles in cardiac stimulation. The timing cycles are very important for proper operation of the implanted stimulation device and to the safety and well being of the patient. Under conditions of cardiac arrhythmias, these timing cycles become even more important and complicated to manage. In the prior art the only information used on-line are the electrical signals sensed by the implanted electrodes, i.e. the intra cardiac electrograms (IEGMs). The difficulty associated with depending solely on the IEGMs stems from the fact that the sensed signals are local and weak, having an amplitude of only several milli-volts with strong coupling from ventricle to atria and ventricle to ventricle. Hence the IEGMs can be misinterpreted by the device controller which can lead to inappropriate pacing.
Implanted cardiac hemodynamic sensors are known in the art and are further developed by several manufactures, mainly for minimal invasive electrophysiological studies. In the last years few cardiac pacemaker devices included such hemodynamic sensors for hemodynamic monitoring and for creating a pacemaker system with a rate response according to hemodynamic sensors.
U.S. Pat. No. 6,865,419 proposes to use an implanted pressure sensor in order to measure the mean pulmonary arterial pressure. U.S. Pat. No. 6,882,882 proposes to use an implanted pressure sensor in order to adjust the atrioventricular delay online.
Prior art US Patent 2003/0158492 A1 presents a method for detection and treatment of myocardial ischemia based on monitoring of both the electrical and the mechanical activity of the heart in order to detect and verify more reliably the myocardial ischemia occurrence. When myocardial ischemia is detected and verified the patent suggests selecting between few options of therapy.
Prior art U.S. Pat. No. 5,458,622 A presents a method for detection, classification and treatment of pathological tachyarrhythmia from physiologic tachyarrhythmia based on implanted activity sensor.
Prior art European Patent 0488512 A2 presents an implantable hemodynamically responsive cardioverting/defibrillating pacemaker. The implantable device uses the information of the implanted hemodynamic sensor during tachycardia to select and control therapeutic means delivered such as antitachycardia pacing (ATP), cardioversion or defibrillation options.
Prior art US Patent 2002/0103442 A1 presents a system and a method for determining mean pulmonary arterial pressure (MPAP) using a pressure sensor located within a ventricle of a heart. The MPAP approximates the mean pressure of the pulmonary artery that can be used to optimize CRT device timings for example.
Prior art European Patent 0541338 A1 presents an implantable monitor/stimulator that monitors and assesses indices of cardiac function and automatically executes physician-selected mode of therapy with ability to increase the strength of contractility of the heart.
The prior art patents cited above use a hemodynamic sensor as a mean to detect specific heart condition (US Patent 2003/0158492), detect and treat cardiac arrhythmias (EU0488512 A2 and U.S. Pat. No. 5,458,622 A) or improve hemodynamic function (US2002/0103442 and EU0541338). The prior art patents cited above do not suggest to use the implanted hemodynamic sensor in order to prevent inappropriate cardiac stimulation or to detect erroneous cardiac events interpretation.
In the present invention a general approach and specific examples are presented that combines information from hemodynamic sensor with the information from the intracardiac electrograms for making a more reliable and safer cardiac stimulation operation. Our approach takes advantage of the fact that implanted hemodynamic sensors are being developed and implemented in implanted cardiac pacemakers and defibrillators in order to improve hemodynamic performance and to be used for future closed loop implanted devices and since such sensors become available, the present invention suggest to further use the complementary data from the hemodynamic sensor as explained in details below.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.